In the operation of blast furnaces hot blast stoves are employed to heat pressurized air that is utilized in the ore reduction process. A mixture of gas and air for combustion is burned in the stoves in a combustion chamber in one part of the stove and the products of combustion passed through flues formed by refractory brick checkerwork in an adjacent part in which the heat is stored for subsequent transfer to the blast furnace process air.
Hot blast stoves of more recent design incorporate a combustion chamber containing a burner integrally formed in the lower end of the chamber to which gas and combustion air are separately conveyed and from which these elements are discharged in a manner to promote mixture for burning in the combustion chamber. Stoves of this type are exmplified by U.S. Pat. Nos. 3,627,284 and 3,642,262 to Van Laar, et al and Vroege, respectively.
As the size and capacity of blast furnaces have expanded, process air of higher temperatures has been required. This has necessitated greater firing rates in the hot blast stoves which the above cited equipment has been incapable of effectively delivering due to the poor air-gas mixing characteristics of the burner design. This deficiency in prior art equipment is compounded when effluent gas from the blast furnace is used as the fuel element since such gas has a relatively low heat content requiring greater amounts to be supplied to the burner in order to achieve the desired firing rates.
It is suggested in U.S. Pat. No. 4,054,409 to improve mixing by introducing the gas and combustion air to the burner through tangentially arranged ports in order to induce swirling of the fluids along concurrent flow paths thereby to improve combustion efficiency. This is not totally dispositive of the problem, however, since, when large amounts of gas, as are required when blast furnace gas is the fuel, are admitted to such burners, air-gas mixing is non-uniform and undesirable pressure pulsations occur in the combustion chamber. These pulsations may be of such magnitude as to cause serious damage to the stove lining, to the checkerwork and/or to the exterior piping and structural supports. To keep the pulsations within acceptable limits it has been required to restrict stove operation which, obviously, has an adverse affect on blast furnace process efficiency.
It is, accordingly, to the solution of such problems that the present invention is directed.